Technical Abstract: Polymer composites have been processed by mixing the component materials at high temperature, in the extruder or compression mold. When agricultural biopolymers, that are usually mixtures of many types of compounds, are used as raw materials, however, high-temperature processes cause unwanted consequences such as decomposition, gas generation, phase separation, etc. This report introduces a new technology to produce biodegradable polymer composites that will potentially replace existing petroleum based polymers. With this newly developed process, polymer composites are produced at room temperature. During the process, micrometer-scale raw materials are coated with zein that has a strong adhesive property, which is then compressed to form a rigid material. Since this technique does not require purification of the raw materials, various types of compounds can be used as component materials. In this report, wheat protein, gluten, was used as a matrix material. The compressive yield strength of the product formed from gluten is ca.43 MPa which is comparable to that of polypropylene.